Update IMU figures, and rotation description

neon/data-collection/data-streams/index.md

@@ -31,16 +31,16 @@
 
 The gaze estimation algorithm is based on end-2-end deep learning and provides gaze data robustly without requiring a calibration. You can find a high-level description as well as a thorough evaluation of the accuracy and robustness of the algorithm in our [white paper](https://zenodo.org/doi/10.5281/zenodo.10420388). 
 
 ## Fixations & Saccades
 
 Available in: <Badge>Pupil Cloud</Badge><Badge>Neon Player</Badge>
 The two primary types of eye movements exhibited by the visual system are fixations and saccades. During fixations, the eyes are directed at a specific point in the environment. A saccade is a very quick movement where the eyes jump from one fixation to the next. Properties like the fixation duration are of significant importance for studying gaze behavior.
 
 ![Fixations](./fixations.jpg)
 
 Fixations and saccades are calculated automatically in Pupil Cloud after uploading a recording and are included in the recording downloads. The deployed fixation detection algorithm was specifically designed for head-mounted eye trackers and offers increased robustness in the presence of head movements. Especially movements due to vestibulo-ocular reflex are compensated for, which is not the case for most other fixation detection algorithms. You can learn more about it in the [Pupil Labs fixation detector whitepaper](https://docs.google.com/document/d/1CZnjyg4P83QSkfHi_bjwSceWCTWvlVtbGWtuyajv5Jc/export?format=pdf) and in our [publication](https://link.springer.com/article/10.3758/s13428-024-02360-0) in *Behavior Research Methods* discussing fixation detection strategies.
 
 We detect saccades based on the fixation results, considering the gaps between fixations to be saccades. Note, that this assumption is only true in the absence of smooth pursuit eye movements. Additionally, the fixation detector does not compensate for blinks, which can cause a break in a fixation and thus introduce a false saccade.
 
 The downloads for gaze mapping enrichments ([Reference Image Mapper](/pupil-cloud/enrichments/reference-image-mapper/#export-format), [Marker Mapper](/pupil-cloud/enrichments/marker-mapper/#export-format)) also include mapped fixations, i.e. fixations in reference image or surface coordinates respectively.
 
@@ -86,18 +86,22 @@
 
 A fusion engine also combines these values with magnetometer readings to estimate the module's absolute orientation relative to magnetic north and gravity as a quaternion. Note that in order to obtain precise absolute yaw readings, the magnetometer needs to be [calibrated](/data-collection/calibrating-the-imu/).
 
-The IMU is located in the top bar of the module and is sampled at 110 Hz. Its coordinate system is oriented with the x-axis pointing to the right, the y-axis pointing in front, and the z-axis pointing upwards.
+The IMU is located in the top bar of the module and samples at 110 Hz. Its coordinate system is oriented with the x-axis pointing to the right, the y-axis pointing in front, and the z-axis pointing upwards.
 
 ![IMU Coordinate System](./imu-xyz-black.jpg)
 
 When relating data from the IMU to things visible in the scene camera, it may be necessary to align their respective 3D coordinate systems. The IMU's coordinate system is rotated by 102° around the x-axis in relation to the scene camera's coordinate system.
 
-![IMU Scene Camera](./imu-scene_camera-black.jpg)
+![IMU Scene Camera](./imu-scene-camera-black.jpg)
+
+::: tip
+Note that leftward rotations in the IMU coordinate system are positive, whereas they are negative in the scene camera and 3D eye state coordinate systems.
+:::
 
 ### Euler Angles
 
 When exporting recordings from Pupil Cloud or Neon Player the IMU's orientation in Euler angles (i.e. roll, pitch, and yaw) is also available.
 
 Pitch is defined as a rotation around the x-axis with a value range of -90° to +90°. Yaw and roll are rotations around the y- and z-axis, respectively, with value ranges of -180° to +180°.
 
-![IMU Pitch, Yaw, Roll](./imu-pitch_yaw_roll-black.jpg)
+![IMU Pitch, Yaw, Roll](./imu-pitch-yaw-roll-black.jpg)